The ability to structure and pattern silicon is important for many applications. There has been particular interest in patterning silicon to make nanostructures. Relevant information regarding silicon fabrication processes known to those of skill in the art can be found, for example, in Sami Franssila, Introduction to Microfabrication (John Wiley & Sons, 2004), and the references cited there. Information regarding common techniques for the deposition of metals on silicon is found in Ronald A. Powell & Stephen Rossnagel, PDV for Microelectronics: Sputter Deposition Applied to Semiconductor Manufacturing (Academic Press 1999).
Semiconductor nanowires have become the focal point of research over the last decade due to their interesting physical, chemical and biological properties. There is particular interest surrounding silicon nanowires, as silicon is one of the most abundant materials in the earth's crust and has become a cornerstone for many of the electronic, optoelectronic, electro-chemical and electro-mechanical devices upon which designs are based.
Silver-assisted etching of silicon has the potential to produce nanowires and other useful nanostructures. The present assignee has described ways of carrying out such etching, for example, in U.S. Published Patent Applications Nos. 2009/256134 and 2010/92888. In certain processes, nanoparticles are dispersed over the surface of a silicon-containing substrate, silver is deposited on top of the nanoparticles, the result is placed in an etchant containing HF. Nanowires are formed where the nanoparticles were placed.
In silver assisted etching processes, it has been found that the quality of the silver film influences the quality of the resulting nanostructures. It has also been found that residual silver left after the etching has potential uses. There is therefore a need for methods which can produce better silver films on silicon substrates.